In a drilling operation, such as in a rotary drilling operation, a drilling fluid is forced down the drill string, about the drill bit at the bottom of the borehole and then back up to the surface. The drilling fluid employed in such a drilling operation usually is an aqueous drilling fluid and is compounded of various materials in order to impart certain desirable physical and chemical properties to the drilling fluid. For example, there is usually incorporated in an aqueous drilling fluid a hydratable clayey material, such as a bentonite clay, to impart desirable viscosity and gel strength properties to the drilling fluid so as to better enable the drilling fluid to carry away the drilling cuttings from the bottom of the borehole. Other materials such as weighting agents, e.g., barium sulfate, are employed to increase the density of the drilling fluid so as to make the drilling operation more effective and safer by overcoming the fluid pressure within the formation being drilled. Other materials such as water loss improving agents, e.g., carboxymethylcellulose, hydrolyzed starch, etc. are added to reduce the loss of fluid from the drilling fluid into the formation during the drilling operation. Still other materials such as corrosion inhibitors, bactericides and drill bit lubricants are incorporated in the drilling fluid in order to improve the drilling operation and the drilling fluid.
Although a wide variety of aqueous drilling fluids containing materials designed to increase the lubricity of these fluids have been proposed and used in the field such as: vegetable oils including soybean and rice oil; tall oil; sodium salts of petroleum sulfonic acids and resin acids (see U.S. Pat. No. 4,064,056); polyethoxylated tetralkylacetylenic diols; and, an ester of thio-bis alkanols and alkenyl succinic acid or anhydride (see U.S. patent application Ser. No. 277,053 filed June 24, 1981 of common assignee), it remains essential that lubricity of said drilling fluids be further improved to reduce the energy requirement of said drilling and abrasion of the drilling equipments.
It is therefore an object to provide an additive composition for drilling fluids that reduces its drilling torque.